Increasing the drains (bifilar coils) voltage from 24V to 42V still does not return the crackling sounds.A mild whispering is all i can detect together with some shown oscillations on the scope.I tried all kinds of combinations of frequency, pulse width and delays.

Could it be that the present setup with 900V Cree MOSFETs and 14A drivers is to beefy for the effect to occure (like avalanching or so)?

First screenshot shows the gate signals (yellow and Blue) of the 2 MOSFETs (220ns delay), and the drain signals (green and purple) of the same MOSFETs with attached bifilar coils.To be noticed is that allthough the gates are switched 220ns apart, the drains show a timed switching.I would have expected that we would see also a delayed switching on the drains (220ns apart).(yellow and green are MOSFET 1, blue and purple MOSFET 2).

Second screenshot shows more delayed gate signals (700ns apart) and again the timed drain signals.

So the delayed gate signals do not translate directly to a delayed drain signal, is it the tramsformer function of this bifilar coil causing this?

Hmmm, i went back to using the 2x IRFP260N MOSFETs driven my a single dual MOSFET driver IXDD604 with 42V on the drains, but no more crackling is heard here too.It looks like boxing up Peters box has tamed the crackling as that is the only change i did.

I will continue to do some sweeping, but up till now no crackling pulses / oscillations are noted.